Synthesis
The synthetic route is summarized in Scheme 1. The yield of the target compound is between 38% and 88% with 4-heptafluoropropylaniline as the starting material. The structure of the target compound was confirmed by 1H NMR, 13C NMR and HR MS. Details of all target compounds are listed in the supporting information. Annotated: Q is selected from phenyl and its substituted derivatives; X=Cl, Br; Abbreviations note: Tetrabutylammonium hydrogen sulfate (TBAHS), N–bromosuccinimide (NBS), N-Chlorosuccinimide (NCS), N,N-Dimethylformamide (DMF), Acetonitrile (ACN), Tetrahydrofuran (THF), Dichloroethane (DCE), N,N-Diisopropylethylamine (DIPEA).
Structure-activity Relationship
Preliminary assessments of the insecticidal activities of all target compounds were performed against P. xylostella, M. separata and N. lugens. The results were listed in Table 1. The insecticidal activities of cyproflanilide was also evaluated under the same conditions.
The insecticidal activities of all the target compounds against P. xylostella, M. separata and N. lugens were preliminarily evaluated. The results were listed in Table 1. The insecticidal activity of Cyproflanilide was also evaluated under the same conditions. In addition, the activity of compound 16a against P. xylostella and M. separata was significantly higher than that of the control compound and equivalent to Cyproflanilide, so the determination concentration was reduced for comparison, and the results are listed in Table 2.
Insecticidal assay
The tested insects P. xylostella, M. separata and N. lugens were provided by Green Tech Laboratory. The insecticidal activities of title compounds against M.separata were tested by immersion method. The insecticidal activities against P. xylostella were tested by leaf-dip method, and the insecticidal activities against N. lugens was were tested by rice seedling immersion method .
On test organisms grown in a greenhouse, all biological experiments were conducted. In accordance with statistical specifications, the bioassay was repeated at 25±1 °C. The mortality rates were adjusted using Abbott’s method, and assessments were conducted on a dead/alive basis. The experiments have a 5% error rate.
Table2. The insecticidal activities of the compound 16a, known compounds and cyproflanilide.
Compounds
|
The 3-days mortality(%,mg/L)
|
P. xylostella
|
M. separata
|
2
|
1
|
2
|
16a
|
97
|
93
|
100
|
Ⅰa
|
0
|
0
|
0
|
Ⅰb
|
0
|
0
|
0
|
Cyproflanilide
|
100
|
100
|
100
|
Annotated: The 3-day mortality(%) = (The number of dead pests /Total number of pests treated)×100%.
Insecticidal Activities Against P. xylostella
Some compounds displayed certain insecticidal activity against P. xylostella, but their insecticidal activity was inferior to Cyproflanilide (Fig.1.5). When Q was phenyl, X was Br and 4-position substituents were H, CF3, CH3, F, Cl, I and CN corresponding compounds 11a, 15a, 17a, 18a, 19a, 20a and 21a showed 0%, 100%, 0%, 100%, 100%, 0% and 77% insecticidal activities at 200 mg/L, showing the sequence 18a > 19a = 15a > 21a > 11a = 17a = 20a, respectively, revealing that 4-F-phenyl exhibited the best insecticidal activity. When Q was changed to 4-F-phenyl and modified with different substituents, compounds 22a and 23a showed 100% and 50% insecticidal activities at 200 mg/L, showed the sequence 22a > 23a. And When Q was pyridyl, X was Br and 6-position substituents were H, CF3 and CN corresponding compounds 12a, 14a and 16a showed 100%, 0% and 100% insecticidal activities at 200 mg/L, showed the sequence 16a > 12a > 14a, respectively, revealing that 6-trifluoromethyl-pyridyl exhibited the best insecticidal activity. Then, the Bromine substituent is substituted by chlorine. Compounds 11b, 12b, 13b, 14b, 15b, 16b and 17b showed 10%, 50%, 90%, 0%, 95%, 90% and 0% insecticidal activities at 200 mg/L, showing the sequence 15b > 13b = 16b > 12b > 11b > 14b = 17b, respectively. The conclusion is that 6-trifluoromethyl nicotinyl group and bromine play a key role in showing the best insecticidal activity. Compounds 11a, 15a, 16a, 18a, 19a and 22a showed 100% insecticidal activity at 200 mg/L, and the activity of compound 16a against P. xylostella was significantly higher than that of the control compound and equivalent to Cyproflanilide
Insecticidal Activities Against M. separata
Some compounds displayed certain insecticidal activity against M. separata, but their insecticidal activity was inferior to Cyproflanilide. When Q was phenyl, X was Br and 4-position substituents were H, CF3, CH3, F, Cl, I and CN corresponding compounds 11a, 15a, 17a, 18a, 19a, 20a and 21a showed 0%, 95%, 0%, 100%, 90%, 0% and 0% insecticidal activities at 200 mg/L, showing the sequence 18a > 15a > 19a > 11a = 17a = 20a = 21a, respectively, revealing that 4-F-phenyl exhibited the best insecticidal activity. When Q was changed to 4-F-phenyl and modified with different substituents, compounds 22a and 23a showed 100% and 0% insecticidal activities at 200 mg/L, showing the sequence 22a > 23a. And When Q was pyridyl, X was Br and 6-position substituents were H, CF3 and CN corresponding compounds 12a, 14a and 16a showed 35%, 0% and 100% insecticidal activities at 200 mg/L, showing the sequence 16a > 12a > 14a, respectively, revealing that 6-trifluoromethyl-pyridyl exhibited the best insecticidal activity. Then, the Bromine substituent is substituted by chlorine. Compounds 11b, 12b, 13b, 14b, 15b, 16b and 17b showed 0%, 10%, 85%, 0%, 90%, 40% and 0% insecticidal activities at 200 mg/L, showing the sequence 15b > 13b > 16b > 12b > 11b = 14b = 17b, respectively. The conclusion is that 6-trifluoromethyl nicotinyl group and bromine play a key role in showing the best insecticidal activity. Compounds 16a, 18a and 22a showed 100% insecticidal activity at 200 mg/L, and the activity of compound 16a against M. separata was significantly higher than that of the control compound and equivalent to Cyproflanilide